Fibrous structural material and method and apparatus for making same



Sept. 10, 1946. J L A 2,407,548

FIBROUS STRUCTURAL MATERIAL AND METHOD AND APPARATUS FOR MAKING SAMEFiled Aug. 1, 1940 3 Sheets-Sheet l g5 CARDING lNVENTOR ATTORNEYS Sept.10, 1946. GOLDMAN 2,407,548

FIBROUS STRUCTURAL MATERIAL AND METHOD AND APPARATUS FOR MAKING SAMEFiled Aug. 1, 1940 5 Sheets-Sheet 2 INVENTOR ATTORNEY Sept. 10, 1946. J.GOLDMAN 2,407,548

FIBROUS STRUCTURAL MATERIAL AND METHOD AND APPARATUS FOR MAKING SAMEFiled Aug. 1, 1940 3 Sheets-Sheet 5 nllllllllllllllllll @716: INVENTOR wB ATTO R N EYS Patented Sept. I 10, 1946 METHOD AND APPARATUS FOR MAKINGSAME Joseph Goldman, New Brunswick, N. 3., assignor to Fibre ProductsLaboratories, Inc., a corporation of New Jersey Application August 1,1940, Serial No. 349,311

This invention relates to fibrous structural material and method of andapparatus for making same. It relates especially to structural materialfabricated by bonding together unspun fibers into integral coherentsheet material.

It is a purpose of this invention to provide structural material madefrom unspun fibers that has very high strength for its weight andthickness. Thus, according to preferred embodiments of this invention astructural web or sheet can be made from cotton fibers, for example,that has greater tensile strength for a given gauge than non-ferrousmetals, such as aluminum and mag-- nesium metals, and has much greaterstrength, e. g. twice as much strength for a given weight as suchnon-ferrous metals.

Features of this invention relate to the method, to the apparatus and tothe product. From the point of view of the method it is onof thefeatures of this invention that unspun fibers which have been broughtinto such disposition in web material that they are predominantly in onedirection are bonded together while the fibers of the web material areunder tension, thereby setting the fibers not only as disposedpredominantly in one direction but also in a condition of tensionedstraightness. Other features of this invention relate to the stepsutilized in connection with the bonding step including the steps wherebythe fibers are straightened and oriented predominantly in one directionby tensioning and drawing so that when the fibers are bonded togetherthe fibrous striated web material will have been conditioned in a mannerespecially suited for the bonding step. Other features of this inventionrelate to the manufacture of unspun fibrous web material during theconditioning steps and bonding step and in directing the web materialfrom the conditioning step to the bonding step.

Certain apparatus features of this invention relate to the meansemployed for drawing and bonding under tension in web form unspun fibersand for handling the web material between the drawing and bonding steps.

The product of this invention is a unique web or sheet material that isof great value for a number of commercialpurposes as a structuralmaterial. The product of this invention in its elemental form is a thincoherent striated web of cobonded unspun fibers which is useful per seand is also useful as 9, ply sheet in the formation of composite sheetmaterial e. g. compris ing a plurality of thicknesses or layers of theelemental web material. a feature of the prod- 27 claims. (ohm- 1) notis the disposition and straightness 'of the fibers in the elemental webwhereby high strength i to weight of fiber and web thickness is secured.The web material also has high resistance to sions.

It is a feature of this invention that the fibers in the unspun fibrousweb material are disposed so as to take full advantage of the strengthof the fibers. According to this invention a multiplicity of the unspunfibers are straightened out so as to be disposed substantially at theirmaximum length when tensioned lengthwise and are likewise bondedtogether for the most part in one direction or nearly so in a sheet orweb that is very uniform in its fiber density and thickness even insheets of relatively large lateral dimen- The method and the apparatusare instrumental in achieving the uniformity of the striated webmaterial, for while the fibers may be originally in theform of sliversor the like, fibers are caused to be distributed very uniformly as byrepeated lapping and drafting operations until the fibers occur in adense striated web of substantially uniform fiber density and thicknessthroughout. The fibers are cobonded in this dense and uniform fibrousweb or sheet so that the bonding effect is very uniform throughout thelateral extent and thickness of the web material. Furthermore, anywrinkling tendency incident to drafting is compensated for by aspreading step to insure uniformity of the striated web I material whenthe bonding material is applied to the web. In this manner a structuralmaterial that not only has high strength, but also has very uniformstrength characteristics throughout, is afforded that renders thematerial suitable for numerous structural applications wherein a strongand light structural material is desired that can be made uniformlythroughout to 7 close specifications.

In order to afford a better understanding of the practice of thisinvention, it will be described for purposes of exemplification inconnection with the fabrication of unspun cotton fibers into thincoherent web material of high strength and density, reference being madeto the accompanying drawings, wherein Fig. 1 is a diagrammaticrepresentation ofa plant layout of machinery for making the unspun webmaterial according to this invention,

Fig. 2 i a diagrammatic side elevational repreing apparatus,

Fig. 4 is a side elevationalview partly in section of the apparatus ofFig.3 and of means for applying the bonding material,

Fig. 5 is a perspective view of one of the spreader bars used inconnection with the apparatus shown in Fig. 4,

Fig. 6 is a top view of an elemental web of unspun fibrous material madeaccording to this invention,

Fig. 7 is a top view of a portion of the web material of Fig. 6 on avery greatly enlarged scale,

Fig. 8 is a transverse cross-sectional view of a portion of the web on avery greatly enlarged scale on the line 8-8 of Fig. 6,

Fig. 9 is a longitudinal sectional view of the web material on a verygreatly enlarged scale on the line 99 of Fig. 6,

Fig. 10 is a plan view on a reduced scale of a composite sheet materialthat embodies this invention,

'Fig. 11 is a side elevational view of a modified form of apparatus forspreading under tension a drawn web,

Fig. 12 is a cross section of the spreading apparatus on the line l2-I2of Fig. 11,

Fig. 13 is a cross section of the spreading apparatus on the line |3I3of Fig. 11,

Fig. 14 is a cross section of the spreading apparatus on the line I l-I4of Fig. 11,

Fig. 15 is a modified form of drafting means that may be used in thepractice of this invention, and

Fig. 16 is a further modified form of drafting means that may be usedaccording to this invention shown in association with part of aspreading means.

Forthe purpose of affording a specific example of the practice of thisinvention in the manufacture of a highly desirable product, cotton fibermay for example be used which fiber contains about 70% of fiber that isabout an inch or more in length although other grades of cotton may beused. Before the bonding step the un- 4 running yard of the cottonfiber. Thefiber is next subjected to. a drawing operation in somesuitable device which may for example be a sliver lapping machine whichis indicated generally by the reference character 26. In this machineabout 20 of the slivers 24 for example may be taken from cans 25 andpassed while, arranged side by side between a series of drafting rolls21.

A series of three pairs of rolls may be used with spun fibers are actedupon so as to distribute them uniformly in a sheet or web so as to bearranged predominantly in one direction and straightened. This treatmentcan be accomplished using different types of apparatus, the type ofapparatus varying depending largely upon the type of fiber beinghandled. For cotton fibers that for the most part are about one inch inlength the treatment is preferably accomplished by repeated drafting andlapping operations whereby the fibers are drawn predominantly in onedirection and are straightened and at the same time are averaged so asto result in a web material having a high degree of uniformity.

A convenient arrangement of apparatus for producing a web comprisingunspun cotton fibers of the character mentioned is shown in Figs. 1 to5. The fiber stock e. g. fiber that has been cleaned and made into apicker lap may first be passed through a conventional carding machinewhich is indicated generally by the reference character 20 in Fig. 1 andwhich may comprise such conventional parts as a licker-in 2|, a cylinder22 and a doffer 23. The sheet material from the carding machine iscondensed into a sliver 24 that is received by any suitable means suchas a can 25. The sliver thus produced may for example containapproximately grains per the nips of adjacent pairs of rolls spaced fromeach other by a distance that is'slightly greater than the length of thefibers. Each pair of. rolls is operated at a speed that is differentfrom the immediately preceding pair ofrolls so that the fibers in theslivers 24 are drawnsufficiently to straighten'them somewhat and arrangethem so that at least partially the fibers become disposedlongitudinally of the fibrous material passing through the draftingrolls. For example the last drafting roll may rotate so that theperipheral speed is twice the peripheral'speed of the first pair ofdrafting rolls in the series and so that the fibrous mass will be drawnapproximately 2 to 1. If 20 slivers each containingabout ,50 grains perrunning yard are run into the sliver lapping machine the fibrous webmaterial that is discharged from the drafting rolls will contain about500 grains per running yard. The web 28 which is discharged from thedrafting rolls is approximately 10 inches in width and may be passedbetween calender rolls 98 and rolled up into aroll 29. The roll 29 canbe removed from the lapping machine and taken to the ribbon lappingmachine which is indicated generally by the reference character 30 andwhich subjects the fibers to a further drafting operation.

In the ribbon lapping machine the web material 28 from each of four ofthe rolls 20 that are carried by the ribbon lapping machine is passedbetween drafting rolls 3|. These drafting rolls may be similar to thedrafting rolls 2'! except that in this case the speed of the rolls isadjusted so that the drafting will be about 4 to 1. Thus if each of thewebs 28 contains about 500 grains of cotton per running yard that entersthe drafting rolls 3| the web discharged from each of the sets ofdrafting rolls will weigh about 125 grains per running yard. In theribbon lapper four pairs of rolls in each set of drafting rolls may forexample be used. The webs discharged from the drafting rolls 3| arepassed through bookfolds 32 which cause the four Webs to becomesuperposed and the superposed webs are passed between calender rolls 99to form a composite web 33 which, according to the present example,would contain about 500 grains of cotton per running yard and would be10 inches in width. The web 33 is then made up into the roll 34.

By the foregoing operations the fibrous sliver material from the cardingmachine has been drawn to an extent of about 8 to 1 and the web 33discharged from the ribbon lapping machine corresponds to an average of80 slivers. The web material taken from the ribbon lapping machine istherefore very uniform in fiber structure and has also been treated sothat the fibers have been arranged for the most part in one directionand then straightened considerably so that the fibers instead of beingin the form of bends and crimps are fairly well straightened. Inasmuch,however, as there is no binder applied to the web the fibers tend in aconsiderable degree to assume their natural curved and crimped state. f

The foregoing operations are largely ofa prefibrous material for thesubsequent operations. In order to complete the manufacture of thestructural material the web material 33 from roll 34 is fed into anotherdrafting frame which is indicated generally by the reference character35. This draftingframe may be of the general type referred to above andmay comprise five pairs of drafting rolls 36, the nips of which arespaced apart by a distance slightly greater than the maximum fiberlengthof'the fibers being handled. The drafting rolls 36 are operated atsuccessively increased speeds as the web material passes between them soas to further draw out the fibers in such a way as to straighten themand arrange them in one direction. The drafting may be carried on sothat in the drafting frame 35 the web material 33 is drafted about 4to 1. If the web going into the drafting frame weighs about 500 grainsper running yard the web that is discharged from the drafting frame 35will contain about 125 grains of fiber per running yard of the webmaterial which is about inches wide as it is discharged from thedrafting frame.

The drafting rolls 36 (and the drafting rolls 21 and 3|) may be providedwith suitable means for adjusting them both laterally and vertically soas to secure desired action. Moreover, the rolls may be fluted orcovered with special materials such as leather, impregnated fabric, corkor the like to augment the drawing action.

As the striated web material is discharged from the drafting frame 35 itis not permitted to relax but while maintaining at least some degree oftension thereon is passed between the applicator rolls 31. These rollsmay apply material adapted to bond the fibers of the sheet togetherwhich material may be a temporary bonding material or a permanentbonding material. The bonding material may be carried in troughs 38which supply the bonding material by feed rolls 39 (driven by anysuitable means not shown) that uniformly deposit the bonding material onthe rolls 31. The rolls 31 may for example be covered with some materialsuch as a fabricwhich carries the desired amount of the binder materialand applies itto the web material 33 as it passes between rolls 31. Ifdesired and depending somewhat on the type of binder material applied,doctor blades llil may be associated with the rolls 31 to control theamount of binder material carried to the bite between the rolls.

Between the drafting frame 35 and the applicator rolls 31 are means forspreading somewhat the sheet material that is discharged from thedrafting frame 35. ,The sheet material as discharged from the draftingframe 35 may for example be 10 inches in width. I have found that it isdesirable to spread the sheet 33 that is discharged from the draftingframe 35 before'a bonding material is applied to the fabric. For examplethe sheet 33 may be spread laterally from a width of about 10 inches asit is discharged from the drafting frame to a width of about 14 to 18inches as it passes between the applicator rolls 31. To accomplish thisspreading action any suitable device may be used.

One device for laterally spreading the web material that is dischargedfrom the drafting rolls 3B which I have found to be effective and theaction of which is readily controllable is shown in Figs. 3, 4 and 5. Byany suitable supporting means such as support members 40 and 4| rolls42, 43, 44, 45 and 46 are carried in suitable bearings. The rolls aredriven from a power driven sprocket wheel 41 by means of a sprocketchain 48 that passes over sprocket wheels 49, 50, 5|, 52 and 53 whichare carried for rotation with rolls 42, 43, 44, 45 and 45 respectively.The peripheral speed of roll 42 is caused to be slightly greater thanthe speed at which the fibrous web material is discharged from the setof drafting rolls 36.

The peripheral speeds of rolls 42, 43, 44, 45 and 46 are successivelysomewhat increased so that the web material 33 is continuously subjectedto tension. This may be done either by making the sprocket wheels 49,50, 5|, 52 and 53 successively somewhat smaller or by utilizing rollswhich successively have increased diameters. Placed between the rolls42, 43, 44, 45 and 46 are spreader bars 54, 55, 56 and 51 which aresecured to ro-.

tatably mounted bars 58, 59, 60 and 6! so that by rotating the bars thebowed portion 62 of the bars can have its position in the path of theweb material between rolls 42, 43, 44, 45 and 46 adjusted as desired soas to avoid all contact with the web material or so as to exercisemaximum spreading action on the web material. By any suitable means notshown the spreader bars 54, 55, 56 and 51 may be locked in the desiredposition. In Fig. 5 one of the spreader bars, i. e. bar 56, is shown.This bar has approximately a semicircular bowed portion "62. The bars 54and 55 are curved somewhat more sharply adjacent the sides than towardthe center, this being the case particularly with bar 54. It has beenfound desirable to commence the spreading action at the sides andgradually extend the spreading action to the center of the web 33 inpassing successively over the spreader bars. For convenience in makingadjustments the spreader bars can be made of material which hassufficient flexibility to permit them to be curved to the shape: thataffords the desired results.

The spreading action takes place by moving the web material undertension over the bowed portion 62 of the spreader bars thereby tendingto spread the web laterally. The primary tension is exerted by the roll46 which has associated therewith a press roll 63 that imposes itsweight upon the sheet 33 passing between it and the roll 46 so that thedrag on the sheet 33 will be more positive. The spreading apparatusdisposes the web material so that it is presented more evenly to theapplicator rolls 31 and tends to remove any longitudinally extendingripples that may be in the web material as discharged from the draftingrolls 36. Preferably the spreading is merely sufficient to remove theripples and cause the Web to lie flat without substantially pulling thefibers laterally away from each other. The drafting andspreadingoperation can be carried out at any suitable speed. In ordinarypractice the web material is preferably passed from the drafting rollsto the applicator rolls at a speed of about '70 to feet per minute. Theweb material may be moved out of the other drafting operations atapproximately a similar speed. It is also possible to secure substantialspreading action without employing the spreader bars inasmuch as the webmaterial tends to spread laterally when passed over a plurality ofrollers. The spreader bars serve to accelerate this spreading action,however.

Continuing the foregoing example of this invention the bonding togetherof the unspun fibers in the web material by means of a casein bindermaterial will be described. The web material is caused to pass from theroll 46 between the applicator rolls 31 the peripheral speed of which issomewhat greater than the peripheral speed of roll 46 so that the.tension on the web material 33 will be maintained. The rolls 31 can I beconveniently driven as by causing the chain 43 driven by sprocket wheel41 to pass over sprocket wheel I04 that rotates with one of the rolls31.

While casein solution might be applied by rolls 31 I have found that itis preferable in obtaining a uniform application of casein as a binderto first apply a temporary binder, which may be merely water.Accordingly water 64 is placed'in troughs 38 and is carried over thesurface of rolls 39 and 31 to the web 33, preferably enough water beingcarried to form small beads 65 at the bite of the rolls 31. Ifdesireddoctor blades l! may be associated with the rolls 31 or otherequivalent means may be used to control the amount of binder, temporaryor otherwise, applied to the in the condition of tensioned straightnessthat they are in upon reaching the applicator rolls.-

In this operation therefore the fibers of the fibrous web are bondedwhile the fibers of the web are in the condition that they occupy whenthe web is under tension. As above mentioned the fibers have beenoriented so that for the most part they are in one direction,particularly the longer fibers and are loosely associated so that theycan be drawn out and straightened without rupturing the fibers or theweb. These fibers are drawn out to maximum tensioned straightness andwhile still-thus drawn out are bonded together.

The application of the temporary binder is followed by the applicationof a permanent binder while the bonding eifectof the temporary binderpersists. The permanent binder may be applied by another pair ofapplicator rolls 66 which have a peripheral speed substantially that ofrolls 31 and to which the binder material in troughs 68 may be suppliedby feed rolls 61. The supply of bonding material can, if desired, becontrolled by doctor blades I02 or by other equivalent means. Forconvenience in handling the web material after leaving the applicatorrolls 31 the material may drop to traveling conveyor 69, over rolls 10,1| and 12 and thence to the applicator rolls66. While the tension on theweb 33 may be momentarily relaxed during this handling of the webmaterial the temporary binder (e. g. water) maintains the fibers in theweb in substantially the same condition that they were in whentheypassed between the applicator rolls 31. Preferably, the rolls 10, 1| and12 are power driven so as to liftthe web material against its own weightand again subject it to tension, and these rolls preferably are drivenat successively increased speeds and at a rate such that the peripheralspeed is slightly greater than the peripheral speed of rolls 31 so as toaugment the tensioning effect in the direction of the fibers. Moreover,the rolls 66 are driven at a rate such that the peripheral speed isslightly greater than the peripheral speed of roll 12 so that the web iscarried into these rolls under slight tension. The peripheral speed ofrolls 66 may conveniently be about .5% greater than the peripheral speedof rolls 31 for example. Similarly the rolls contacting the web materialsubsequent to rolls 66 are preferably driven at successively slightlyincreased peripheral speeds (e. g. a small fraction of one percentincrease) until the binder is set in a setting step, e. g. in chamber14, or .during drying, e. g. in chamber 15. In this way the web materialis prevented from wrinkling during its travel through the apparatus andany tendency of the fibers to relax, before the bonding material hasset, to a non straightened condition is minimized with the result thatthe fibers in the web, after the bonding material has set, will still besubstantially as straight as'when they were introduced into the bondingstep. The conveyors 63 and 13 may be of any desired length so that thetime interval during which the web material rests thereon may becontrolled as desired. Alternatively the conveyors may be drawn by anysuitable means not shown so as to travel more slowly than the speed atwhich the web material is deposited thereon so as to plait the webmaterial thereon and thereby increase the period of time during whichthe web is carried thereby.

The permanent binder that is applied may be a 20% solution of solublecasein, for example. Due to the preliminary moistening of the web byapplicator rolls 31, the casein solution applied by applicator rolls 66impregnates the web material very uniformly and evenly so that the webwill retain about 25%, for example, of thecasein (dry weight) on the dryweight of the fiber.

It remains to dry the bonded web material and if desired subject it tosome further treatment. To this end the web material may fall from theapplicator rolls 66 to a carrier 13 and thence to a, treating chamber or'zone 14. From the treating chamber the fabric can pass to a dryingchamber or zone 15 in which it may pass over a plurality of heateddrying rolls 16 until the moisture in the web has been reduced to about10%. The treating chamber 14 may be omitted if desired. The treatingchamber is shown, however, in order to illustrate that the bonded webmay be treated in any way that may be desired. For example, the caseinbonded fibrous web above de scribed may be subjected to some gaseous orliquid environment which may be introduced into the chamber from jets11. For example formaldehyde gas or tannic acid solution may be appliedto the bonded web to insolubilize the casein. After the bonded webmaterial has been dried it can be made up into a roll 18 and isavailable for any purpose. In addition to drying the web on drying rollsit may be dried in festoons or on a carrier that is passed through adrying chamher or in any other suitable way.

Web material that has been made as above described is shown in Figs. 6,7, 8 and 9. In Fig. 6 a fragment of the material is shown andillustrates the predominant straightness and unididirectionalcharacteristics of the fibers. If the fibrous material is examined undermagnification it appears somewhat as shown in Fig. 7, namely the fibershave one predominant direction. This is especially true with regard tothe longer fibers 19 inasmuch as some of the shorter fibers [whichusually occur in cotton fibers as commonly sold may be disposed withsomeirregularity as indicated. This is due to the fact that it is thelonger fibers that are acted upon most vigorously in the draftingoperations and which are drawn to tensioned straightness when the web ismaintained under tension in the direction of the fibers. The smallamount of miscellaneously disposed short fibers doesnot, however, impairthe great strength of the web material in the predominant fiberdirection and acts as a filler that to a slight degree augments thestrength of the web material in a lateral direction. Figs. 8 and 9indicate the disposition of the fibers in a dense coherent mass with thelong fibers l9 essentially unidirectional. The indication of the fibersin Figs. 6, 7, 8 and 9 is largely continuous-web more than 1 fiberdiameter in thickness. No attempt is made to indicate in Figs. 8 to 10the presence of the binder inasmuch as the binder in the fabric will bepresent in different ways depending primarily upon the amount of thebinder. If the binder constitutes about 25% or less of the material bydry weight,

the binder is distributed for the most part on r the surface of thefibers and acts to bond the surface of the individual fibers to thesurface of adjoining fibers. Inasmuch as the fibers are straightenedandare essentially unidirectional the binder in the amount used is mosteffective inbonding the fibers together. The fibers instead of beingbonded together at only a few points of contact as is the case withmiscellaneously disposed fibers, are brought into intimate contact andeach straightened fiber becomes bonded over most of the surface thereofwith adjoining substantially parallel fibers that are likewise straight.If larger amounts of binder are employed the fabric becomes morecompletely dominated by the binder component while still retaining theinherent advantages of I the fiber base for the material.

Due to the conditioning steps wherein a large number of slivers arelapped and drawn the web material is very uniform in thickness and fiberdensity and binder distribution affording uniform high strengththroughout.

In the example above given the cotton fiber contained over about 70% offiber that is one inch or more in length. Of course, other grades ofcotton fiber may be used. In order to achieve the advantages of theinvention in marked degree, however, over about 50% of the cotton fiberstock should be of an inch in length, and preferably over 60% to 70% ofthe cotton fiber should be over inch in length. Fiber material whichcontains about 50% or more of fibers at least about inch in length isregarded as long fiber. The percentages of fiber given above andelsewhere herein and in the claims are percentages by weight.

The characteristics above mentioned of the structural web are thosewhich result from manufacturing steps above described wherein ordinarycotton fibrous stock is used and wherein the stock is subjected to adrawing of about 32 to 1 in preparing it for the bonding step. In suchcase, as above mentioned, some of the shorter fibers remain somewhatindiscriminately disposed. It is possible, however, by subjecting thefibrous web material to repeated drafting and lapping operations priorto the bonding step to cause substantially all of the fibers to becomestraightened and arranged in one direction. For certain uses of thefinished material this may be desirable but for most purposes it is notnecessary to obtain such a high degree of fiber straightnessandarrangement in one direction. The occurrence of miscellaneouslydistributed fibers may likewise be eliminated by subjecting the cottonto a combing operation using any suitable type of combing machinedesigned for handling cotton fibers of .which many are known,

the shorter fibers being largely eliminated by the combing step so thatthe drafting operation it substantially tensioned straightness,namelm'the I straightness that the fibers assume when stretched taut,and are arranged approximately in one direction, e. g. within about 15of the mean direction of those fibers that are for the most part in onedirection. In this type of fabric web about of the fibers over A. of aninch in length are among those fibers which are arranged approximatelyin one direction and are substantially of tensioned straightness.

As aforesaid the extent to which the cotton fibers are drawn dependslargely upon the type of fabric that is to be produced. Thus for websthat when made up are to be quitelight and are to ex bit greatuniformity of texture and very high strength in the direction of thefibers the elemental web material may be subjected to the conditioningoperation until about of the fibers are disposed substantially in onedirection and exhibit tensioned straightness as they are led to thebonding step.

On the other hand the drawing may be discontinued when only a majorproportion of the fibers are disposed in one direction and exhibittensioned straightness. This can be accomplished for example by takingthe material discharged from the sliver lapping step which has beenabove described and in which the fibers are drawn about 2 to 1 to afforda web weighing about 500 grains per running yard, and then passing thematerial through the drawing frame 35 on which the fibrous sheet isdrawn 4 to 1 and thence to theapplicator rolls 3! so that the fibrousmaterial will be drawn a total of 8 to 1. Such a fabric web is not asuniform as a fabric web which has been subjected to additional lappingand drawing steps before the fibrous material is bonded together. In anysuch web material it is preferable that the major proportion of thefibers that are arranged approximately in one direction and arestraightened, include at least about 70 of the fibers that are overabout of an inch or more in length.

'A fibrous web which has only approximately 50% of the fibers disposedin one direction and straightened by tension nevertheless exhibits greatstrength. Such a web is especially useful in making relatively heavysheet materials containing a plurality of the elementalwebs, e. g. about8 to 20, thereby minimizing any lack of uniformity in the elementalwebs. Even with such heavy composite fabrics, however, it is preferableto draft the fibrous material prior to bonding until about 70% of thefibers is straightened by tension and are approximately in onedirection. A fabric which contains about 800'grains of cotton fiber persquare yard and which contains about 200 grains per square yard ofcasein binder, for example, has a tensile strength of about 50 poundsper inch in each direction when the individual webs are disposed withthe preponderant fiber direction of half the webs at a right angle tothe preponderant fiber direction of the other half of the webs and whenin each web about 50% of the fibers are bonded while straightened in onedirection by tension. This compares with a .tensile strength of about 25pounds per inch in each direction for a fabric containing the sameweights of fiber and of casein binder which is made by weaving cottonthreads so that about equal weights of fiber are in the warp and theweft. If in the material embodying this invention 70% of the fibers ineach web are disposed substantially in one direction and arestraightened, then even greater strength, e. g. 75 pounds per inch ineach direction, can be attained. A

Somewhat more generally web material composed of unspun fibers cobondedin the manner referred to can readily be made according to thisinvention so as to, have a tensile strength of at least about pounds perinch width for each 100 grains per square yard of fiber and preferably atensile'strength of at least about 20 pounds per inch width for each 100grains per squareyard of fiber. These tensile strengths can be obtainedusing other binders than casein in an amount sufilcient to preventlongitudinal relative slippage of the fibers when the sheet material issubjected to tension in the preponderant direction of the fibers.

Another feature of the web material is that in addition to being strongit can be made so that it y is highly resistant to stretching. Cottonfibers,

per se, are substantially non-stretchable. According to the presentinvention .the fibers are subjected to tension which straightens themout and they are bonded together while very uniformly and evenlydistributed in this state. Therefore sincethe fibers are substantiallystraightened the material does not stretch when subjected to tension inthe direction of the fibers but remains substantially unyielding.Moreover, since a preponderant proportion of the fibers are disposed inone direction, the load is borne by all of these fibers as well as bythe binder, thus affording great strength in resisting rupture. When theper square inch and preferably at least about 20,000 pounds per squareinch.

In the practice of this invention I have found that it is distinctlypreferable, especially in connection wth cotton fibers to bond thefibrous material which has been arranged in one direction and has beenstraightened by tension, while the fibers are disposedin thin elementalstriated Somewhat more generally the striated web material should be ofsufiicient thickness so that the fibers at least in major proportionwill be obtained in juxtaposition when oriented to tensionedstraightness and approximately in one direction, and should preferablybe in thickness about 2 to about 8 times the diameter of the fiber thatis used. 8

When it is desired to make heavier material this can be done bylaminating or plying the elemental webs until a sheet of desiredthickness and weight is produced. The fibers in the elemental webs arepreferably bonded together before being assembled 'in a composite sheetand may be made up into a composite sheet by bonding together websinwhich the fibers have previously been cobonded together.

In Fig. 10 there is illustrated afcomposite sheet which includeselemental webs 8 l' and 82 in which the preponderant fiber directionextends longitudinally of the sheet. If desired the composite sheet caninclude a web 83 in which the fibers extend transversely so as to givetransverse strength binder that is used is.also substantiallynonstretchable very strong structural web materials can be obtained.

The .web material made according to this invention ispreferably denseand compact for the weight of fib'er contained therein. Thus, a webmaterial which contains about 200 grains of fiber per square yard can bemade of such compactness and fiber density that .the web will be onlyabout one-thousandth of an inch or less in thickness. By fiber density"the weight ofthe fiber per square yard per unit thickness is intended.

in the elemental web form or in the form of a composite sheet containinga plurality of elemental webs can be made so that the ratio of thicknessin thousandths of an inch to weight of fiber, in grains per'square yardis. about 1 to 200.

While such materials are preferable, even those materials according tothis invention wherein the ratio of thickness in thousandths of an inchto grains per square yard is only about 1 to 100 are very dense ascompared with materials heretoto the composite sheet as a whole. In suchcase the presence of the transverse sheet 83 tends to keep the fibers inwebs 8i and 82 from spreading and thereby increases the strength of thematerial in the fiber direction of the webs 8| and 82 so that thestrength in this direction is somewhat greater than if the web 83 werenot included. The number and fiber direction of the fibrous webs can bewidely varied and it is anadvantage of this invention that means areafforded whereby strength in the direction or directions of greateststrains can be attained with The structural material of this inventioneither minimum of fiber material.

The nature and amount of the bonding agent that issued can be variedwidely dependingupon the type of material to be produced. For mostpurposes binder to the extent of about 20% to 50% by weight (dry) of theweightpf the fibers is incorporated with the fibers especially whenthebinder is relatively inelastic or non-plastic at ordinary temperatures.Lesser amounts, e. g. about 10%, is sufficient for many purposes. On theother hand, 50% to may be used if highly impregnated fibrous material isdesired. The use of amounts of'binder as highas about 100% may bedesirable, e. g. in the production of waterproof material in which thebinder is a natural or synthetic rubber material or a bituminousmaterial.

The particular bonding material that is selected is largely optional.'Among bonding materials applied in an aqueous medium there are, inaddition to casein'above mentioned, numer- 13 ous others such as glue,latex, asphalt emulsions and the like. When the bonding agent is appliedin an aqueous medium it is preferable to first apply water to theelemental web material as a temporary binder so that the permanentbinder ing step a wetting agent may be employed such as pine oil soap,and the like, in order to promote more uniform impregnation of thefabric with the permanent binder. Moreover, reactive materials such ascoagulants may be incorporated in the first application, e. g. acoagulant such as alunr, tannic acid, formaldehyde, etc., may beincluded to insolubilize or harden the permanent binder subsequentlyadded.

.When the binder is added in an aqueous medium subsequent treatment ofthe web is largely confined to drying, although before, during, or afterdrying the web may be subjected to further treatment, e. g. in atreating chamber such as chamber 14.

Other bonding materials such as bitumens, cellulose esters, celluloseethers, synthetic resinous materials and the like, may be applied whendissolved in an appropriate solvent therefor. When a volatilenon-aqueous solvent such as naphtha, acetone, etc., is used subsequentevaporation of the solvent in a suitable solvent recovery system, ispreferable. When a volatile non-aqueous solvent is employed thetemporary bonding step may be omitted. In this'case the binder solutioncan be applied by applicator rolls 31, for example. However, it isfrequently desirable especially when the binder material isrelatively'tacky as applied, to first incorporate a small amount of atemporary binder, e. g. about 1 to 2% of starch, silicate of soda,methyl cellulose or the like and thereafter apply the permanent binderas 21. separate step.

Binder materials which are thermoplastic may likewise be employed byapplying them in a heat liquefied condition or by applying them in afinely divided condition and then heating the fibrous web material torender the incorporated thermoplastic material sticky and bond thefibers together. Thus, bitumens such as asphalts, pitches, tars, etc.,-cellulose esters and cellulose ethers such as cellulose acetate,cellulose nitrate, ethyl cellulose, benzyl cellulose, etc., a widevariety of synthetic and natural resins such as urea-furfural resins,vinyl resins, etc., may be employed. The binder material may be areversible thermo plastic such as asphalt which after application may besoftened by reheating or may be thermosetting such asphenol-formaldehyde resins of the Bakelite type. After the fibers havebeen cobonded-by the thermoplastic binder in a tacky or sticky conditionit is usually sufficient merely to permit the web material to cool untilthe binder is substantially non-sticky.

The flexibility or pliability of the structural web or sheet materialwill depend largely upon the character and amount of binder that isused. Thus a web or sheet containing about 50% of the weight of thefiber of a relatively rigid binder such as a rigid synthetic resinbinder of the phenol-formaldehyde type will be quite stiff especiallywhen a plurality of the individual ply sheets are made up into acomposite sheet of considerable thickness. Binders of the celluloseester m 14-:-- or ether typeafford structural sheet materials ofintermediate stifiness. Structural sheet material comprising.relativelysoft binders such as low softening pointbituminous'materials, rub- -ber and the like can be made which are verypliable.

7 While reference has been made to'the employment of a'bonding materialwhich remains on the surfaces of the fibers it is also possible to treatthe fibers with a material that attacks them sumciently so that'thesurface becomes sticky and bonded and then removing the material butleaving the fibers bonded together. Thus, in

the case of cotton fibers the fibrous web may be treated with sulphuricacid, zinc chloride or the like, e. g. by the applicator rolls 31,Theadded material that attacks the fiber may thereafter be neutralizedor washed away by suitable means, the extent of the action beingdependent upon the time interval during which the material in activecondition remains in contact with the fibers prior to neutralizing it orwashing it away. Any

- such material, since it results in bonding the fibers together, isregarded herein as a bonding material.

Where a plurality of the elemental webs are combined to form a compositesheet this can be done in several ways. For example, the web materialafter having been bonded while the web is under tension can be laminatedwhile the bonding material is adhesive so that the webs will adheretogether. Alternatively, the bonding material as a result of evaporationof solvent, cooling and the like may be permitted to harden andthereafter the web materials may be bonded together. If the bondingmaterial can be reactivated, e. g. by heating a reversible thermoplasticthe webs have been laminated so that it may penetrate sufficientlythrough the composite sheet to bond the laminations togethen Anotherdesirable way to bond the elemental webs together is to dispose finelydivided thermoplastic material such as asphalt, cellulose esters orethers, resins or the like between superposed webs and then subject thecomposite sheet to heat as by passing it between or over rolls heatedsuflicient to render the thermoplastic material tacky and bond the webstogether.

Whether the sheet material is in theform of an elemental web or acomposite sheet it is preferable asaforesaid to employ only about 20% to50% of the weight of the fiber of binder that remains incorporated withthe sheet material. The fibers that are arranged approximately in onedirection and are of substantially tensioned straightness will have anytensile load in the direction of the fibers distributedamong them, andexcess of binder tends to detract from the strength of the material perunit weight rather than otherwise since the fiber is usually strongerthan the binder material. The amount of binder that is appropriate forcementing the fibers is all that is required and since the fibers are in15 a dense compact arrangement the amount binder required is relativelysmall.

It is to be understood that the foregoing operation whereby theimprovements of the invention may be attained merely constitute anillustrative example of the practice of this invention and that thedrawing or drafting can be performed in other ways and that thespreading of the fibrous web, if the spreading step is performed, can becarried out by other means. Thus, in Fig. 11 there is shown analternative device that may be employed for spreading the i1- brous webbetween the drafting and the application of the bonding material. Inthis modification the web material in passing from the drafting rolls 36to the rolls 31 passe over a saddlebacked part I03 which is downwardlycurved and is bowed outwardly, e. g. as indicated in the cross-sectionalviews shown in Figs. 12, 13 and 14. The peripheral speed of the rolls3'! is slightly greater. than the-peripheral speed of the last of thedrafting rolls 36 so that the web material 33 is maintained undertension in passing over the part I03 which because of the curvaturethereof causes the web 33 to spread, e. g. from about inches asdischarged from the drafting rolls to about 14 to 18 inches when the webreaches the applicator rolls. It is apparent that equivalent means maylikewise be employed.

In carrying on the spreading step the extent of the spreading willdepend somewhat on the material being handled. For cotton fibers it isusually desirable to spread the material prior to the bonding step byabout 25% to 75% of its original width. Especiallywith heavier fiberswhich tend to be more uniformly distributed as discharged from thedrawing apparatus less spreading, e. g. about 10% to 25% of its originalwidth is usually sufiicient prior to the bonding step.

The bonding material can also be applied in other ways, for example, asillustrated in Fig. 11, As shown, the bonding material is sprayed ontothe web 33 before it goes between the rolls 31 from nozzles I06. Thismethod of application of bonding material is especially suitable when arelatively small amount of bonding material is to be applied.v It isalso possible to seize the conditioned web material while the fibers aredrawn to tensioned straightness and thereafter apply the bondingmaterial, e. g. through a foraminous restraining member. Alternativelya. thermoplastic binder such as asphalt may be blown into the web 33 inpowdered form from the nozzles I00 and the rolls 31 may be heated tosoften the asphalt and bond the fibers in the web material together.Various other ways of applying binder are also possible although formost pur-- poses the ways above described have been found to bepreferable.

straightening the fibers and arranging them in one direction. The extentof the drafting in each drafting frame and the sequences of lapping maybe varied widely although the fibers should not 16bearrangedtoothicklyinordertoobtain agood drawing action.

For drafting fibers that are longer than cotton fibers modifiedequipment is desirable such as that shown in Figs. 15 and 16 which maybe a gill box or draw box or the like. There are a number of relativelylong fiber materials e. g. bast fibers such as jute, sizal, hemp, ramie,flax, and coir, or natural silk. In mtking web material from such fibersthe fibers are preferably caused to Occur in lengths averaging about 6to Sinchesandthefibersinthisforrhairecarded and run into heavy sliverform. The slivers, e. g. two, may be run for example into the gill boxshown in Fig. 15 comprising the sliver guide II, the retaining rolls '2and 33, the slip roll 84, the drawing roll and pres roll I5. The rollsI3 and 35 are spaced apart by a distance that is greater than the lengthof the fibers and between them are the movable fallers 81 on the pins ofwhich the fibers are carried from the roll I3 to the roll 85. Thefallers move at a speed that is somewhat greater than the peripheralspeed of the roll 83. The drawing roll 35 may have a peripheral speedabout 4 times that of roll 33 thereby drawing the fibers by about 4to 1. Any suitable means (not shown) such as screw means may be used tomove the fallers, lower them at the end of their travel toward roll 85,return them and elevate them at the end of the return travel.

It is usually desirable to subject the fibrous material to furtherdrafting. In such case the web material discharged from rolls 85 and 85maybemadeupintoarollll orifdesiredmay be passed to sliver form.Apparatus for carrying on a second drafting operation is shown in Fig.16 which includes the retaining rolls so and SI, the slip roll 92, thedrawing roll 53 and the press roll 94. The roll of material 33 feedsinto the rolls 36, 3| and 52 andis carried bythe fallers 35 to rolls 93and 94. The fallers travel at a speed somewhat greater than theperipheral speed of roll SI and roll 33 has a peripheral speed about 8times the peripheral speed of mll 3| thereby drawing the fibers about 8to 1. If desired one or more webs, e. g. from roll 88' in ad dition toroll 33, may be fed into the device of Fig. 16 so that the fibrous webwill not become excessively attenuated by the drafting. Alternativelyone or more slivers may be fed into the device of Fig. 16 as may bedesired.

In the device of Fig. 16 the fallers l5 are carried in the form of acontinuous belt about rolls 3i and 31. Theactionisessentiallythesam asthe action of the fallers in the device of Fig. 15 and the devices ofeither Figs. 15 or 16 may be used although the device of Fig. 15 issomewhat preferable. The different mechanisms are shown primarily toillustrate the fact that the drafting mechanism may take many differentforms. It is preferable however when the fiber is subjected to more thanone drafting operation that the pins on the fallers used for anydrafting after the first drafting be somewhat more numerousthanthepinsonthe fallersusedinthefirst drafting Operation.

After the fibrous web material has passed from rolls 33, 33 it is takenover spreading means such asthatshowninFigs.2to5 orinFlg. 11 forexampleto means for app ying bonding material while maintaining the webmaterial imder tension as it travels from the rolls 33, 34 to the meansfor applyin the bondin material.

By way of example two very heavy slivers of 17 jute fiber weighing about1200 grains per running yard may-be into the drafting appa ratus of Fig.wherein it is drawn about lto 1 toformweb material aboutll'inches wideweighing.600 grainsper running'yard. Fourof'the webs thus made (weighingin all about 2400 grainsper running yard) are then run to the draftingapparatus shown in Fig. 16 wherein the fibrous web material isdrawnabout 8 to l to form aiweb material about 11 inches wide weighing about300 grains per running yard. Thislatter material is thenspread to about15 inches in width before the bonding materialis applied. The bondingmaterial may be any of those de scribed above and used insimilarproportions. The bonding material may be applied by any of themeans heretofore referred to or the equivalent thereof. For 'suchverycoarse fiberthe web preferably weighsabout- 400 to 800 grains per squareyard when the bonding material is applied. a I l The process can also becarried out inconnection with fibers of intermediate length suchas wool,in which the fibers may run about 2 or 3 inches in length. In such casea drawbox or gill box or the like may be usedto straighten the fibersand arrange them in one direction but, of course, the spacing betweenthe retainer rolls and the drawing rolls will beless than when longerfibers such as jute, hemp, etc., are used.

Any operation or apparatus forv drawing fibers, by some such action asdrafting rolls, gill box, or draw box wherein fibers are seized andpulled out essentially in one direction thereby straightening them inone direction, is referred to herein as a drafting operation orapparatus and is to be distinguished from mere sheet-forming actionssuch as felting or the action of a carding machine.

In addition to fibers such as those above mentioned, other fibers may bemade up into web structural material e. g. synthetic fibers such asrayon, cellulose acetate and the like. Web structural materialconsisting wholly or partially of mineral fibers e. g. asbesto fibersmay also be made according to this invention." In cobonding mineralfibers cobonded into striated web material any suitable binder thereforsuch as sodium silicate may be employed. Moreover, fibers which areunspinnable, e. g. kapok, mil-kweed fibers, manila, Spanish" moss andthe like, can be made up into structural material according to thisinvention.

Regardless of the character of the fiber that is employed it isdesirable that the proportion of the fiber that is arrangedapproximatelyin one direction and brought to tensioned straightness correspondsubstantially with the proportions above mentioned in connection withcotton fibers for the reasons mentioned in connection with the foregoingdescription of web materials and composite sheet materials made fromcotton In the, practice of this invention the web material can betreated in various ways during the performance of the method. Thus, theweb ma: terial can be treated with a dye or stain or pigment during theapplication of either the temporary or permanent binder or as a separateoperation. Moreover, waterproofing or waterrepeilent material maysimilarly be incorporated. If desired, afiller material such as finelydivided clays (bentonite, kaolin, etc.)', silica dust or the H like maybe incorporated ina similar way.

In the foregoing description a web material about 14 to 18 inches wideis described. It is. of course, pos'sibleto make the webrinaterialjofother widths; This can be done by varying the lateral capacity of the"equipment usedfeijg. equipment such as described above. It is preferablethat web material during the draftingoperation be at least Qinchesinwidthand that the drafted striated webmaterial be at least about 12inches inwidth when the fibers are integrally cobonded; Formaking'wideweb material it is also possible to mount a plurality of the unitsin parallel and operate them simultaneously at the samespeed, the outputof each unit being placed alongside the output of an adjacent one,"Thus. a, P111- rality of the drafting frames;35can be placed side byside and the web material discharged from each spread laterally untilthe marginal edges abut each other. The wide web can then be passedbetween a common pair of applicator rolls for applying the bondingmaterial. If fibers from a cardirig machine or the like areused as asource of fibrous material it is not necessary to pass the carded sheetto sliver form, inasmuch asthe carded material in sheet form may besubjected'to repeated lapping and drafting operations to conditionfibrous material in themanner above referred, to. e

In order to obtain material having uniform density and thickness so asto achieve a product having uniform strength characteristics throughout,it is desirable to make at least two ribbonor sheet-like intermediatewebs and then lap.

them and subject the composite web to drafting to attenuatethe compositeintermediate web and draw the fibers thereof to increased straightnessing. Preferably at least four such intermediate web or sheet-like bodiesare made and lapped so'as to obtain a drafted web that is very uniform.1 d

It is apparent fromthe foregoing that fibrous structural material havinggreat strength for the weight of the fiber can be produced according tothis invention in a very economical way. Fabriclike sheet materialhavingthe strength of woven fabrics can be made without going through thecostly operations of spinning and weaving, Moreover, sheetmaterialresembling sheet metal in strength per gauge thickness can be made andnection with certain specific embodiments thereof it is to be understoodthat this has been done merely for the purpose of illustrating thepractice ofthis invention and affording a better un- Accordingly, thescope of this invention is to be governed by the language dersta-ndingthereof.

of the following claims construed in the lightof the foregoingdescription. I

I claim: I

1. Amethod ofmaking afabricated web of co-bonded unspun fibers whichcomprises subjecting unspun fibers to draftinguntil thefibers arepreponderantlystraightened and arranged in one direction longitudinallyof an elongated ping a plurality of said webs to form a composite webcontaining a plurality of web lamina-- tions, subjecting the compositeweb to a drafting operation to attenuate the composite web and draw thefibers to increased straightness in a direction corresponding to thedirection of the drafting while said fibers are in a dry and essentiallyunbonded conditio and thereafter cobonding the fibers together while instriated attenuated web form to form a coherent integrally bonded webmaterial, the fibers not being permitted to relax between the drawingstep and the bonding step.

3. Apparatus for making a web of cobonded unspun fibers which comprisesdrafting means for straightening and arranging the fibers in apredominant direction longitudinally of an elongated web, means spacedfrom said drafting means for applying a bonding material to the fibrousweb after the web is discharged from the drafting means, and means formaintaining said web under tension between said drafting means and saidmeans for applying the bonding material to said web.

4. Apparatus for making a web of cobonded unspun fibers which comprisesdrafting means for straightening and arranging the fibers in apredominant fiber direction longitudinally of an elongated web, saiddrafting means including a plurality of adjacent pairs of rolls betweenwhich said fibers pass and means for driving said pairs of rolls atsuccessively increased speeds to accelerate the movement of said webmaterial and draw the web material longitudinally, applicator rolls forapplying a bonding material to said fibers of said web discharged fromthe last of said pairs of drafting rolls acting on said web, and meansfor rotating said applicator rolls so that the peripheral speed of saidapplicator rolls is at a somewhat greater speed than the peripheralspeed of the last pair of said drafting rolls to maintain said web undertension longitudinally thereof when fed into the nip of said applicatorrolls.

5. In apparatus for making unspun fibrous material, the combination withdrafting means for straightening unspun fibers and arranging them in apreponderant fiber direction, of tensioning means for materialdischarged from said drafting means to tension and means between saiddrafting means and said tensioning means for laterally spreading webmaterial discharged from the drafting means.

6. Apparatus according to claim wherein the spreading means comprises aplurality of rollers over which the web material ,is adapted to pass. 7.Apparatus according to claim 5 wherein the spreading means comprises aplurality of rollers over which the web material is adapted to pass andmeans between said rollers for bowing out the center of the web materialas it passes besubjecting said fibrous web laterally.

8. Apparatus according to claim 5. wherein the spreading means comprisesan elongated centrally bowed part over which the fabric is adapted topass and thereby become spread laterally.

9. Apparatus for making a web of cobonded unspun fibrousmaterial whichcomprises drafting means'for straightening said fibers and arrangingthem in a preponderant fiber direction in an elongated striated web,said drafting means including a plurality of adjacent pairs of rollsbetween which said fibers pass and means for.

driving said rolls at successively increased speeds to accelerate themovement of said web as it passes successively between said rolls anddraw said web material longitudinally, means for spreading said webdischarged from the last pair of drafting rolls laterally upon beingdischarged from said drafting means, applicator means for applying abonding material to the web, and

. means for maintaining said 'web material continuously under tensionduring the travel thereof between said drafting means and said applicator means.

10. Apparatus for making a webof cobonded unspun fibers which comprisesdrafting means for producing an attenuated webin which the fibers have apreponderant fiber direction, a pair of rolls, means for carryingsaidweb .of material under tension in said fiber direction suflicient tostraighten the fibers in said direction between said drafting means andsaid rolls and means for applying bonding'material to said web receivedby said rolls after said web is discharged from said drafing means andwhile said fibers are in said condition of tensioned straightness.

11. A method of making structural sheet material which comprises forminga striated web of loosely associated contiguous fibers about 50% ofwhich are at least about inch in length, in which about 70% of thefibers at least inch in length have a preponderant mean direction andare disposed within about 15 of said mean direction and in which thefibers are arranged in substantially uniform thickness and fiberdensity, subjecting said web material to pulling tension in saiddirection at a first zone while said web is restrained at a second zoneso as to prevent movement of said web at said second zone at a rate thatis as great as the rate at which said web is pulled at said first zone,saidfirst zone being spaced from said second zone by a distance greaterthan the length of the rection between said first and second zones to bedragged relatively to contiguous fibers and become tensioned andstraightened while in an essentially unbonded striated web form, andbonding said fibers of said web together before said pulling tensionimposed on said web is relaxed to form a coherent integrally bondedsheet material of substantially uniform fiber density and binderdistribution throughout wherein said fibers brought to said condition oftensioned straightness as aforesaid are maintained in said condition bysaid binder after said pulling tension is relaxed.

12. A method of making structural sheet material comprising unspuncotton fibers, which comprises carding cotton fibers about 50% of whichare at least inch in length, then drafting the carded cotton fibers todraw the fibers fibers in said web, thereby causing said fibers disposedin said ditaining said fibers in acondition of tensioned straightnessand longitudinally of the sheetlike body during the travel of the fibersfromthe nipof said rolls, and thereafter, and, while so drawing saidsheet-like body with said fibers in said condition of tensionedstraightness, bonding the said fibers of said sheetlike body together byapplication of a binder thereto to form a coherent integrally bondedsheet material wherein said fibers are fixed in said condition oftensioned straightness by the said binder so applied thereto. v

13. A method according to claim 12 wherein the cotton fibers after thecarding step are, subjected to the drafting to draw and partially orientand straighten the fibers in the direction of the drafting and wherein aplurality of bodies of the so drawn and partially straightened fibersare lapped and then subjected to further drafting prior to the finalstep wherein the fibers in a sheetlike body are fixed by application ofbinder thereto while travelling in a condition of tensloned straightnesslongitudinally of the sheetlike body, the total drawing accomplished bythe drafting steps subsequent to carding being at least 32to l.

14. A method according to claim 12 wherein the fibers when drawn intothe bonding step are disposed in a sheetlike body weighing between I-and400 grains per square yard and are drawn by gripping the sheetlike bodybetween the nip of a second pair of rolls which pull individual fibersand drag them relative to other fibers in frictional contact therewithso as to tension said fibers and dispose said fibers in tensionedstraightness in the sheetlike body when the binder is applied to cobondthe fibers together into a coherent sheet material.

15. A method according to claim 12 wherein the fibrous sheetlike body ismaintained under longitudinal tension after the binder is applied andduring setting of the bonding material applied to the fibers.

16. A method of making a fabricated sheet of cobonded unspun fiberswhich comprises arranging the fibers in an elongated body, andsubjecting the fibers while in elongated body form to drafting to drawthe fibers at least 8 to 1 in the direction of the drafting and orientthe fibers in the direction of the drafting in a sheetlike body whereinthe fibers are straightened in said direction longitudinally of thesheetlike body, said sheetlike body being drawn under tension in thefinal stage of drafting into and between the nip of a pair of rollerswhich grip the material of the sheetlike body therebetween. drawing saidsheetlike body of fibers from the nip of said pair of rollers undertension and with dragging of individual fibers disposed longitudinallyof the sheetlike body relative to contiguous fibers in frictionalcontact therewith, thereby disposing and maintaining said fibers in saidsheetlike body in a condition of tensioned 22 straightness during thetravel of the sheetlike body from the nip of saidrollaand, .whileflsodrawing said sheetlike body with said'fibersin said condition ortensionedstraightness bondlng the said fibers of said sheetlike bodytogether to formna coherent integrally bonded sheet mate rial whereinthe fibers are fixed in co-bonded relation insaid condition of tensionedstraightness. l I l b N '17. A method of making afabricated sheet of icobonded unspun fibers which comprlsessub je'ctingunsp'un fibers looselyassociated in dry non-co-bonded conditionto drafting in a, sheet- .likebody wherein the fibers are positively straightened by gripping the,fibers between I draftingrolls-and by drawing the sheetlike body bysaid rolls while the fibrous material of said taining the fibers in acondition of tensioned sheetlike body is restrained at a distancegreaterthan the length of the fibers from the nip of said rolls,therebyorienting said fibers in the direction of travel of saidsheetlike bodyand straight ening the fibers in said directionlongitudinally of the sheetlike body, the drafting accomplishing adrawing of at least 8 to 1, then further drawing and attenuating saidsheetlike body of fibers by gripping the sheetlike body between rollswhich are rotatedat a peripheral speed that draws the fibers in saidnon-co-bonded condition and as oriented by the drafting with dragging ofindividual fibers disposed longitudinally of the sheetlike body relativetocontiguous fibers in frictional contact therewith; therebymainstraightness during the travel of the sheetlike body to said lastmentioned rolls, and first 8 131 plying a binder to bond said fiberstogether immediately adjacent said last-mentioned rolls and prior todischarge of said fibers fromthe nip of'said last-mentioned rolls,therebyfixing said fibers in cobonded relation in said condition oftensioned straightness in a coherent sheet,

18. A method according to claim 1'? wherein the fibrous sheetlike body,afterleaving the rolls last mentioned in claim 17 adjacent to which thebinder is applied, is subjected to tension during the setting of thebinder.

19. A method of making a sheet of co-bonded unspun cotton fibers whichcomprises forming a thin striated sheetlike body of fibers which arearranged approximately in one direction and a major proportion of whichare substantially straight, drawing said sheetlike body in the directionof said straightened fibers while said fibers are in non-co-bonded drystate with dragging of said fibers relative to other fibers infrictional contact therewith to maintain said fibers in" straightenedcondition, and, while so drawing said sheetlike body, applying a firstbinder material thereto to fix said fibers in said straightenedcondition in said sheetlike body, and then applying further binder tosaid sheetlike body while said fibers are maintained in saidstraightened condition by said first binder material to additionallybond said fibers in straightened condition into a coherent andintegrally bonded sheet material.

20. A method according to claim 19 wherein said first binder is waterand said further binder material is a non-volatile adhesive substanceand is applied in an aqueous medium to said web while the fibers in saidweb are still moist.

21. Structural sheet material comprising a web of unspun fibers at leastabout 50% of which are inch or more in length, said web beingcharacterized by the fact that at least about of the fibers of inch ormore in length are disare maintained in a condition 23 posedapproximately in one direction, are of substantially tensionedstraightness, are substantially non-stretchable and iare co-bondedtogether in longitudinally non-slippable relation by a substantiallynon-stretchable binder distributed substantially uniformly about andamong said fibers.

22. Structural sheet material in the form of a rigid, hard, dense body,said structural material consisting primarily of unspun fiber andbinder, at least 50% of the fiber component being fibers of inch or morein length, and said structural material being characterized by the factthat at least 70% of the fibers over inch in length of tensionedstraightness by said binder and are disposed in approximately the'samedirection in each individual layer of one ormore layers comprised insaid structural material, and said structural material being furthercharacterized by the fact that said binder for said fibers is asubstantially nonstretchable binder that is distributed substantiallyuniformly about and among said fibers, and the fiber'density in saidstructural material being suchthat the ratio of thickness in thousandthsof an inch to weight of fiber in grains per square yard is 1 to at least100.

23. [Structural sheet material according to claim 22 wherein said fiberscomprise cotton fibers and wherein said substantially non-stretchablebinder constitutes about 10% to about 50% by dry weight of saidstructural material and wherein the fiber density is such that the ratioof thickness in thousandths 01 an inch to weight of fibers in grains persquare yard is 1 to at least 200. I

24. Structural sheet material in the form of a rigid, hard, dense body,said structuralmaterial being characterized by comprising a plurality ofintegrally bonded superposed webs of unspun fibers, at least 60% of thefibrous material of said web being substantially unstretchable fibersinch or more in length and at least about 70% of the fibers of inch ormore in length being r 24 I disposed approximately in one directionin'each web and being of substantially tensioned straightness, and saidfibers in each of said webs being co-bonded together by a. substantiallynon stretchable binder material distributed substantially uniformlyabout and among said fibers, the fiber density in said webs. of saidstructuralmaterial being such that the ratio of thickness in thousandthsof an inch to weight of fiber in grains per square yard is 1 to at least200.

25. Structural sheet material according to claim 24 wherein the fibersin said webs are unspun cotton fibers distributed in substantially.uniform thickness in each web so that the fiber in each,

web weighs about to 400 grains per square yard I and wherein saidsubstantially non-stretchable weight of the fibers.

unspun fibers which comprises draftingmeans for producing an attenuatedweb inwhich the fibers have a. preponderant fiber direction in thedirection of the drafting, a pair of rolls arranged for passage of saidweb therebetween after discharge from said drafting means, meansincluding said pair of rolls for drawing said web in said fiberdirection to dispose the fibers in said web in a condition of tensionedstraightness in said web after said web is discharged from said draftingmeans and when said web is fed between said rolls, and means immediatelyadjacent said pair of rolls forapplying bonding material to said webpassing between said rolls while said fibers in said web are in saidcondition of tensioned straightness.

27. Apparatus according to claim 26 which also includes means forsubjecting said web after leaving said pair of rolls thereto to tensionduring the setting of the binder.

JOSEPH GOLDMAN.

with said binder applied

